Antibiotic Management for Appendicitis
Uncomplicated Appendicitis (No Perforation, Abscess, or Peritonitis)
For uncomplicated appendicitis, administer a single preoperative dose of broad-spectrum antibiotics 0-60 minutes before surgical incision and discontinue all antibiotics within 24 hours postoperatively. 1, 2
Recommended Single-Agent Regimens
- Ticarcillin-clavulanate, cefoxitin, ertapenem, moxifloxacin, or tigecycline are acceptable single-agent options for mild-to-moderate community-acquired appendicitis 2
- Piperacillin-tazobactam 3.375g IV is also an effective single preoperative dose 3
Recommended Combination Regimens
- Metronidazole plus cefazolin, cefuroxime, ceftriaxone, levofloxacin, or ciprofloxacin are appropriate combination options 2
- Ceftriaxone 2g combined with metronidazole provides adequate anaerobic coverage, with a maximum daily dose of 2g ceftriaxone 2
Critical Point on Duration
- No postoperative antibiotics are indicated for uncomplicated appendicitis after adequate source control 1, 2, 3
- Prolonging antibiotics beyond 24 hours provides no additional benefit and increases costs, hospital stay, and resistance 2
Complicated Appendicitis (Perforation, Abscess, or Peritonitis)
For complicated appendicitis with adequate source control achieved surgically, limit postoperative antibiotics to 4-7 days maximum, with 3-5 days being optimal. 1, 2, 3
Recommended Broad-Spectrum Regimens
- Piperacillin-tazobactam is FDA-approved for appendicitis complicated by rupture or abscess, covering beta-lactamase producing E. coli and Bacteroides fragilis group 4
- Imipenem-cilastatin, meropenem, or doripenem are appropriate carbapenem options for complicated cases 1, 3
- Ceftriaxone-metronidazole combination is an acceptable alternative regimen for perforated appendicitis 2, 5
Evidence Supporting Shorter Duration
- A recent quality improvement study (2025) demonstrated that ceftriaxone plus metronidazole for perforated appendicitis resulted in comparable surgical site infection rates and 30-day readmission rates compared to broader-spectrum regimens 5
- The study showed superficial SSI rates of 2.8%, deep SSI 0%, and organ space SSI 8.5% with the ceftriaxone-metronidazole regimen 5
Dosing for Complicated Cases
- Piperacillin-tazobactam: 3.375g IV every 6 hours for 7-10 days 4
- Imipenem-cilastatin or meropenem: 1g IV every 8 hours 3
- Ceftriaxone 2g IV daily plus metronidazole 500mg IV every 8 hours 2, 5
Antibiotics to Avoid
Do not use ampicillin-sulbactam, cefotetan, clindamycin, or aminoglycosides as first-line agents. 1, 2
- Ampicillin-sulbactam has high E. coli resistance rates exceeding 20% 1, 2
- Cefotetan and clindamycin have increasing Bacteroides fragilis resistance 1, 2
- Aminoglycosides are not recommended for routine use due to toxicity concerns when equally effective alternatives exist 1
Coverage Considerations
Do NOT Routinely Cover
- Enterococcus coverage is not necessary in community-acquired appendicitis 1, 2
- Empiric antifungal therapy for Candida is not recommended 1, 2
Anaerobic Coverage is Essential
- Ceftriaxone alone is insufficient because it lacks adequate anaerobic coverage against Bacteroides fragilis 2
- Metronidazole must be added when using ceftriaxone, cefazolin, cefuroxime, or fluoroquinolones 2
- All regimens must be effective against enteric gram-negative organisms (E. coli) and anaerobes (Bacteroides spp.) 2
Fluoroquinolone Caution
- Avoid quinolones unless local E. coli susceptibility is ≥90% due to increasing resistance 2
Pediatric Considerations
Children with non-perforated appendicitis should receive a single broad-spectrum antibiotic preoperatively with no postoperative antibiotics. 2, 3
- Cefoxitin or cefotetan are appropriate single-dose options 3
- For complicated appendicitis in children, use the same regimens as adults with weight-based dosing 3
- Early switch to oral antibiotics after 48 hours with total duration less than 7 days postoperatively is recommended 2, 3
Non-Operative Management (Antibiotics Alone)
For patients managed non-operatively, administer a minimum of 48 hours IV antibiotics followed by oral antibiotics for a total of 7-10 days. 3
- IV piperacillin-tazobactam followed by oral ciprofloxacin plus metronidazole is an acceptable regimen 3
- Success rates are approximately 70% at one year, with higher failure rates (≈40%) in patients with appendicolith, mass effect, or appendiceal diameter >13mm 6
- Surgical management should be recommended in fit patients with these high-risk CT findings 6
Common Pitfalls to Avoid
- Do not prolong antibiotics beyond 3-5 days postoperatively in complicated cases with adequate source control 1, 2, 3
- Do not use broad-spectrum agents for uncomplicated appendicitis, as this increases toxicity risk and facilitates resistant organism acquisition 1
- Do not forget anaerobic coverage when using cephalosporins or fluoroquinolones—always add metronidazole 2
- Do not continue postoperative antibiotics for uncomplicated appendicitis after adequate surgical source control 1, 2